Preheat the Oven: Preheat your oven to 350°F (175°C) and lightly grease a donut pan.
Mix Dry Ingredients: In a large bowl, whisk together flour, baking powder, baking soda, pumpkin pie spice, cinnamon, and salt.
Mix Wet Ingredients: In another bowl, combine pumpkin puree, brown sugar, granulated sugar, milk, eggs, melted butter, and vanilla extract. Whisk until smooth.
Combine Wet and Dry Ingredients: Gradually add the wet ingredients to the dry ingredients, mixing until just combined. Be careful not to overmix.
Fill the Donut Pan: Spoon the batter into a piping bag or zip-top bag with the corner cut off. Pipe the batter evenly into the prepared donut pan, filling each cavity about 3/4 full.
Bake: Bake for 10-12 minutes, or until a toothpick inserted into a donut comes out clean. Allow the donuts to cool in the pan for 5 minutes, then transfer to a wire rack.
Add Coating (Optional): While the donuts are still warm, brush them lightly with melted butter and dip them into the cinnamon sugar mixture.